import java.util.Scanner;

public class Practice {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        double a = in.nextDouble();
        double b = in.nextDouble();
        double c = in.nextDouble();
        double d = in.nextDouble();
        double e = in.nextDouble();
        System.out.println((a+b+c+d+e) / 5);
    }
    public static void main7(String[] args) {
        int z;
        Scanner in = new Scanner(System.in);
        int a = in.nextInt();
        int b = in.nextInt();
        int c = in.nextInt();
        z = c/b;
        if (c % b != 0) {
            z++;
        }
        a -= z;
        System.out.println(a);
    }
    public static void main6(String[] args) {
        Scanner in = new Scanner(System.in);
        int a = in.nextInt();
        int i,z=1;
        for (i = 1; i <= a; i++) {
            z *= 2;
        }
        System.out.println(z);
    }
    public static void main5(String[] args) {
        Scanner in = new Scanner(System.in);
        int a = in.nextInt();
        int b = in.nextInt();
        int c = 0;
        c = a + b;
        if (c >= 100) {
            c %= 100;
            if (c / 10 == 0) {
                System.out.println(c%=10);
            } else {
                System.out.println(c);
            }
        } else {
            System.out.println(c);
        }
    }
    public static void main4(String[] args) {
        Scanner in = new Scanner(System.in);
        int a = in.nextInt();
        int b = in.nextInt();
        int c = a / b;
        int d = a % b;
        System.out.print(c + " ");
        System.out.println(d);
    }
    public static void main3(String[] args) {
        Scanner in = new Scanner(System.in);
        int a = in.nextInt();
        int b = in.nextInt();
        int tmp = 0;
        tmp = a;
        a = b;
        b = tmp;
        System.out.println("a="+a);
        System.out.println("b="+b);
    }
    public static void main2(String[] args) {
        int[] arr={1,2,3,4,5,6,7,8,9,10};
        for(int i = 0;i < arr.length ;i++){
            for(int j = i + 1;j < arr.length;j++){
                if(arr[j] % 2 != 0) {
                    int tmp = arr[j];
                    arr[j] = arr[i];
                    arr[i] = tmp;
                }
            }
            System.out.print(arr[i]+" ");
        }
    }

    public static void main1(String[] args) {
        int[] arr = {1,2,2,4,4,3,3,1,5};
        for (int i = 0; i < arr.length; i++) {
            for (int j = i + 1; j < arr.length; j++) {
                if (arr[i] == arr[j]) {
                    arr[i] = 0;
                    arr[j] = 0;
                }
            }
        }
        for (int i = 0; i < arr.length; i++) {
            if (arr[i] != 0) {
                System.out.println(arr[i]);
            }
        }
    }
}